CHARACTERIZING THE TILL-DERIVED WATER CHEMISTRY IN THE SENECA LAKE, NY (USA) WATERSHED

Aqueous geochemical studies of lake water typically focus on natural lakes that record a balance between the regional hydrologic budget and the bedrock geology. Determining the contribution of solutes to lake chemistry from weathering of glacial till requires the characterization of water chemistries from constructed lakes whereby rainwaters can interact with fresh tills and release their cation and anion suites. The Hanley Biological Preserve, located in a rural, agriculturally dominated setting, has undergone significant change in land use from open fields to a landscape dominated by small ponds constructed over forty years ago. Sampling and characterization of water chemistries from these till-lined ponds as well as comparisons to the natural creeks flowing through the preserve and the tributaries and waters of Seneca Lake define the role that tills play in delivering solutes with weathering. The weathering of the till provides a different suite of cations than the local bedrock geology. The weathering of dolomite, high-Mg and low-Mg carbonate provides magnesium and calcium in the till derived waters. In contrast, calcium is the dominant cation in the Seneca Lake tributaries compared to sodium in Seneca Lake. Minor amounts of sulfate present in the till-derived waters suggest pyrite was oxidized to provide sulfate ions. What actual role freshly weathered tills play as a source of solutes in the chemical evolution of lakes remains unknown. Given the widespread nature of tills in the region, it seems reasonable that the initial chemical composition of proto-Seneca Lake, immediately after glaciation, reflected a till- rather than a bedrock-derived cation chemistry.